Another major “green roof” project is set to move forward atop a high-profile building in downtown Minneapolis.

City officials are putting together construction documents for a green roof over Target Center, even as the city – with help from a project team led by RSP Architects – continues the job of planting 40 varieties of mostly native plants on a portion of Minneapolis City Hall.

The Target Center project was first reported by Finance and Commerce in March 2007.

By putting vegetation on top of the 18-year-old city-owned arena, the city hopes to protect the membrane and extend the roof’s life. Green roofs typically last 40 to 50 years, compared to 20 to 25 years for a conventional roof, Guild said.